Activated carbon particles have long been used as adsorbents for gases and for adsorbing liquid and solid organic compounds from liquids in which they are dissolved. They have also been used in the purification of waste waters contaminated with large amounts of dissolved organic matter and many processes for such purpose have heretofore been described. However, each of these prior processes has one or more disadvantages that make it less than eminently suitable for the treatment of industrial waste waters containing high concentrations of dissolved organic contaminants so that the water may be purified at the lowest possible cost.
At least a portion of the organic contaminants that are adsorbed by the activated carbon in processes are generally capable of being desorbed and recovered, if desired, by heating the carbon in the absence of oxygen or oxidizing gases at a temperature between 300.degree. and 500.degree. C. On the other hand, to remove contaminants that cannot be desorbed in this manner or that are decomposed during this treatment forming a carbonaceous residue on the surface of the activated carbon, the spent and thus pretreated activated carbon must be treated with steam, for example, at a temperature of approximately 800.degree. C in order to reactivate or regenerate the carbon for reuse as an adsorbent. During such conventional regeneration treatments, a portion of the activated carbon, amounting to between approximately 5 and 15% by weight of the carbon, upon which such organic compounds had been adsorbed, is converted to volatile products which thereby represent a loss of the carbon. The high loss of carbon that occurs during such generation treatments is obviously a great disadvantage of such processes.
The purification of industrial waste waters containing high concentrations of dissolved organic contaminants by such methods is not practical because the activated carbon quickly becomes saturated with the organic contaminants and is thus spent and does not adsorb any further quantities thereof, as a result of which it must be frequently regenerated, with the accompanying high losses that are incidental to such regeneration treatments.
The activated carbon particles are also often subjected to regeneration before they have been completely spent, that is, have not adsorbed the maximum amount of organic contaminants that they were capable of adsorbing, which also represents a waste or loss.